1. Field of the Invention
The present invention relates to a control device for a machine, having two coupled control sticks or joy sticks intended to be actuated by respective operators.
Although not exclusively, it applies more particularly to piloting devices for aircraft and it will be described hereafter more specially with reference to such an application, it being understood that this in no wise implies the limitation of the scope of the invention.
Numerous machines are known, such as aircraft, helicopters, tanks, public works machines, etc. . . , which are provided with an assembly of controlled elements which may be actuated from one or other of two interconnected control stations, controlled by two separate operators (called pilot and copilot in the case of vehicles) and each equipped with a control member of the joy stick type, mounted for pivoting in any direction. These two control members are connected to the members to be controlled and are mechanically coupled together so that each of said operators has at his disposal the whole of the controls for said members to be controlled and so that voluntarily tilting by direct actuation of one of said control members by one operator causes an identical induced tilting in the same direction or the other.
2. Description of the Prior Art
Up to present the transmission of control orders between a joy stick actuated by an operator and a member to be controlled has taken place mechanically, so that said joy sticks were of relatively large size and capable of withstanding and transmitting considerable mechanical forces. Such joy sticks were therefore adapted to be disposed in front of said operators, held with both hands by each operator and actuated through action of the forearm of this latter, the amplitude and intensity of the movements thereof being conditioned by the resistances to be overcome for operating the mechanical controls.
It will be noted that the use of both hands of each operator not only allowed considerable forces to be transmitted but also made these forces symmetrical and identical for both operators.
However, the mechanical controls are being more and more often replaced by electric controls having numerous advantages, for example in so far as the mass, the cumbersomeness, maintenance, and taking complex control laws into account, etc. . . are concerned. The result is that said joy sticks are connected and associated with electric sensors which detect the positional variations of said joy sticks and which control electric controls actuating said controlled members as a function of the indications from said sensors. Thus, said joy sticks only transmit very small forces and their size and mechanical strength may be considerably reduced. This has led to the design and use of small sized joy sticks called "ministicks", which may be held and actuated by a single hand of an operator.
In addition to the above mentioned advantages concerning the use of electric controls, such ministicks free the space in front of the operators, so as to optimize the grouping together of other controls in front of them, so that each ministick is disposed laterally with respect to said operators. In addition, particularly when the two control stations of the operators are parallel (which is generally the case in a vehicle in which said stations are disposed facing the front thereof), so as to respect the symmetry of the machine with respect to an axis passing between said stations, one of the ministicks is disposed on the left of the left hand operator and the other on the right of the right hand operator. In such a case, the left hand operator holds then the associated ministick in his left hand, whereas the right hand operator holds his in his right hand. Respect for the symmetry of control of the machine results then in asymmetry from the point of view of the operators.
It has been observed that such asymmetry raises difficulties, when the control of the machine requires tilting of the ministicks, laterally from left to right and conversely with respect to said operators. This certainly is due to human morphology which means that the possibilities of exerting a lateral force with the same hand holding a ministick are different depending on whether the force is exerted by pushing with the palm towards oneself or by pulling outwardly with the fingers. Moreover, in the above described arrangement, a pull with the fingers on one of the control sticks corresponds to a push with the palm in the other station.
Thus, not only will the lateral push and pull be felt differently by each operator, but furthermore the asymmetry of forces is reversed when a control with the left hand in the left hand station is taken up by a control with the right hand in the right hand station and vice versa. Passage of the control of the machine from one control post to the other does not then take place smoothly, which may result in serious consequences, particularly in the case of an aircraft.
To overcome these drawbacks, it has already been proposed, in a complex device for the mechanical interconnection of two ministicks, to associate a force sensing device with each of said control members, so that the force sensing device associated with the control member actuated by the left hand is active only when this latter is voluntarily and directly actuated by an operator from left to right, and so that the force sensing device associated with the control member actuated by a right hand is active only when this latter is voluntarily and directly actuated by an operator from right to left.
Such a device for the mechanical interconnection of two ministicks, having complex force sensing devices with selective action, gives satisfaction. However, because of its mechanical structure, it cannot take maximum advantage from the electrically controlled embodiment of the flight controls. In addition, it has considerable play and friction with respect to the range of movement obtained and to the forces brought into play, so that its performances, particularly in so far as piloting precision is concerned, are not as good as might be hoped for.